The invention relates to a water treatment control system, particularly one that integrates the control of various aspects of a water reservoir or stream using various probes and which includes provision for probe failure detection. Modern water treatment requires the use of both physical and chemical processes. They have traditionally been controlled independently. Typical applications of water treatment systems include, but are not limited to, municipal or industrial water treatment plants, cooling towers, swimming pools, agricultural or food processing plants, and carwash systems.
The physical processes include pumping of the water being treated through filters to remove suspended particles and replacement of contaminated water with fresh water. The chemical processes include injection of sanitizers, oxidizers, pH adjustment chemicals, biocides and other chemicals. In addition, heaters or coolers are used to maintain proper water temperature.
All these processes depend on the use of sensors, timers and outputs for control and monitoring, including remote display and operation. Because the equipment is usually made by different manufacturers, each process has an independent control system which results in large, cumbersome installations and a lack of compatibility and an inability to communicate between different instruments.
An object of the present invention is to integrate all the monitoring and control functions into a single control unit using a microprocessor to manage the different processes. Such an integrated control system makes it easy for the operator to supervise all the different aspects of the water treatment system and to respond rapidly to any malfunction or other emergency.
Another object is to access the control unit remotely by modem and computer, and simulate the display remotely of the actual on-site panel for the purpose of monitoring and control from a remote location.
A further object of the invention, using a microprocessor, is the monitoring of water balance conditions through the computation of the saturation index, or Langelier Index, based on water pH, temperature, alkalinity and hardness. This index shows whether the water is properly balanced, or corrosive, or scaling.
Still another object, using a microprocessor, includes a dynamic probe failure test based on recovery analysis of an induced sensor offset condition. This test is more reliable and more general than static probe failure testing used in conventional applications. In particular, it can be applied to any type of sensing element.